Abelisaurus comahuensis was discovered in 1983 by Roberto Abel, a professor from the the Museum of Cipolletti in Argentina.

It was found in the Anacleto Formation in the Lago Pellegrini stone quarries of the Río Negro province of Argentina.

Abelisaurus is a theropod from the Campanian age of the Late Cretaceous, and the first example of the Abelisauridae family. The skull has some similarities to Tyrannosauridae, but there are enough differences that it cannot be included in that family. Going by this information, and other specific species comparisons made by the the authors of the original paper (Novas & Bonaparte), the family Abelisauridae was created for this dinosaur. It is believed that the Abelisauridae family evolved in South America, in parallel with Tyrannosauridae in North America.

The holotype of Abelisaurus comahuensis is known from only a partial skull. The skull is missing part of the lower jawbone, the palate, and some zygomatic bones. No other specimens have been found, so while the general shape of the dinosaur can be theorized, the weight, length, and proportions can only be estimated by comparison to other similar dinosaurs.

It is believed that Abelisaurus comahuensis was a large bipedal theropod, with small arms and slender legs. In 2016, a paper by Orlando Nelson Grillo and Rafael Delcourt revisited the specimens of the Abelisauridae family, and concluded that Abelisaurus measured 7.4m, give or take 0.7m.

Abelisaurus was a carnivore, as evidenced by its teeth.

"Abelisaurus" is to honour Professor Roberto Abel, the former director of the Museum of Cipolletti in Argentina; Roberto discovered the holotype of Abelisaurus comahuensis, which is now stored in the Museum of Cipolletti. "Comahuensis" refers to the region in Argentina where the holotype was discovered, Comahue, which spans three provinces: Neuquén, Río Negro, and the Northern part of Patagonia.